Photographic material



Sep@ 25, E934., A. voN BIEHLER 1,974,524

PHOTOGRAPHIC MATERIAL Filed March 8, 1932 sup/W,

Patented Sept. 25, 1934 UNITED STATES PATENT oFFlcE PHOTOGRAPHICMATERIAL Application March 8, 1932, Serial No. 597,639 In Germany March9, 1931 8 Claims.

My present invention relates to photographic filter layers.

Filter layers for photographic purposes which are, for instance,required in the multi-pack proc- 6 esses of the color photography, areprepared with dyestus which diuse as little as possible, especially ifsuch layers are superposed. The dyestuffs hitherto described, however,are soluble in Water and show an appreciable diffusion when incorporatedin thick, relatively slow drying layers.

I have found that any troublesome diffusion is avoided by iinelydispersing a water-insoluble dyestuff in a binding agent forming thebase of the lter layer. Such binding agents are gelatin, glue, agar-agarand the like water-soluble colloids. When the binding agent has beensufficiently mixed with the insoluble dyestuff, filter layers can beprepared which, after drying, are completely homogeneous andtransparent. The mixing is effected with mechanical means in apparatuswell known to those skilled in the art.

Suitable organic pigments are all of the waterinsoluble organic colorlakes which do not detrimentally influence the light-sensitivephotographic layers. salts, such as the barium or calcium salt and theheavy metal salts, such as the bismuth or especially the lead salt ofacid dyestuffs which are liable to be decolorized in a suitable mannerwithout the silver picture of the photographic material being injured.As dyes suited for the purpose setvforth I enumerate among others theSyrius dyes, Benzolichtgelb (cf. Fierz-David, Knstliche organischeFarbstoffe 1926, page 168), Congo red and Congo blue. The color lakesare prepared according to the methods well known in the art of dyeingwith the difference that the precipitation is effected in the absence ofa substratum. The precipitated color lakes are in the form of a paste orpulp, intimately mixed with the binding agent until a homogeneouslycolored mass is formed. The lter layer can be arranged in, before orbehind the light-sensitive emulsion layer. In the rst case the lightsensitive emulsion is mixed with the color particles. The layer thusproduced can be employed for the production of color pictures madeaccording to one of the direct processes. In the second case the coloredlayer acts as a light filter and is adapted t select light of a certainwave length for the exposure. In the third case, if the lter layer isarranged behind the light sensitive emulsion layer the former acts as ananti-halation layer. I pre- 53 fer, however, to apply my filter layersin front I prefer the earth alkali metall of the light sensitiveemulsion layer or behind the same.

In the accompanying drawing Figs. 1 to 3 show the aforesaidarrangements.

In Fig. 1 the filter layer consisting of a binding 00 agent and a colorlake is provided on the photographic film consisting of a support and alight sensitive emulsion layer. i

In Fig. 2 the color lake is distributed in the emulsion layer which isprovided on the usual support.

In Fig. 3 the filter layer consisting of a. binding agent and a colorlake is arranged between the emulsion layer and the support.

The following' example illustrates the inven- 70 tion:

An aqueous solution of Congo red is mixed with an aqueous solution ofbarium chloride until a precipitate is no longer formed. The precipitateis purified by decanting and then mixed with an aqueous gelatin solutionof 10 per cent strength having a temperature of 40 C. The Wholeisintimately mixed until it assumes the appearance of a uniformly colored,transparent mass. The filter layers are then prepared in the usualmanner by 30 casting. The dyestuif-gelatin layer thus formed istransparent and does not show any diiusion even in a wet state. Bybathing it in an acidied solution of sodium hydrosulphite it can beeasily decolorized.

My invention is not limited to the foregoing example nor to the specificdetails given therein. The quantity of dyestuif to be added to thesolution of binding agent is dependent upon each special purpose and canbe determined by a few simple experiments. Other color lakes than thosementioned can be used with success.. I contemplate as being within thespirit of my invention all such modifications as fall within the scopeof the appended claims.

What I claim is:

1. A photographic filter layer which comprises a color lake of an acidazo dyestui, and a binding agent.

2. A photographic filter layer which com- 100 prises an earth alkalimetal salt of an acid azo dyestuff removable without injuring aphotographic silver picture and a binding agent.

3. A photographic filter layer, which comprises a heavy metal salt of anacid azo dyestui removable without injuring a photographic silverpicture and a binding agent.

4. A photographic lter layer which comprises the lead salt of a Siriusdye and a binding agent, no

5. A photographictilter layer which comprises the barium salt of Congored andgigelatin.A

6. Theprocess of ,producingphotographicilter means of a compoundselected" from the group consisting of earth alkali 'metalsaits'andfheavy metal salts, purifying the precipitate, mixing vtheprecipitate with the solution of a binding agent;

and casting` aniterlayer from the said mixture.

8. The process ofproducing photographic lter layer which comprisesvprecipitating from a solution of Congo-red the Adyestufi -by `vmeans ofbarium-chlorid purifying the precipitate,l .mix-

)ing the precipitate with an aqueous solution or.

gelatin, and casting the lter layer from the said mixture.4

ARPAD v. BIEHLER.

